Our past research indicates that a deficiency in the ability to process global structure information accounts for the historic empirical observations of age decrements in certain tests of perceptual-cognitive ability which are measures of the efficiency of visual information processing. Our general hypothesis is that such a deficiency would be due to decreased efficiency of the "transient" neural channels which are sensitive to low spatial frequencies. Breitmeyer and Ganz have proposed a theory of visual neural channel activity which makes very explicit predictions about what types of interactions occur within and between channels and about how the interactions are exhibited in perceptual tasks measuring very early processing. We propose a series of experiments which will examine the performance of young and old subjects in a series of metacontrast masking and backward masking experiments. Special attention will be given to developing target and mask stimuli with spatial frequency and orientation components designed to optimally test the predictions which should flow from the hypothesized deficit, given Breitmeyer and Ganz's predictions for normal young visual systems. We will also measure contrast sensitivity functions for sinusoidal gratings in different orientations and study the generation of illusory gratings. The experiments provide estimates of the functional efficiency of the transient and sustained channels since the paradigms used should be sensitive to: (a) The interaction of transient with other transient channels, (b) The inhibiting interaction of transient on sustained channels, (c) The inhibiting interaction of sustained on transient channels and (d) The intergrative interactions of sustained with other sustained channels. Data in the expected directions would give support for the general hypothesis and would provide a link between an extensive empirical literature on perceptual-cognitive changes in aging and many recent experimental observations made with elderly persons. The empirical literature has demonstrated a relationship between performance on these tests of cognitive ability and health, life expectancy and iminancy of death.